The present invention relates to a fluid operated torque tool for, and a method of tightening a nut onto a plate with a washer there between.
More particularly, the present invention relates to a fluid operated torque tool for, and a method of tightening a nut onto a plate with a washer there between, to be used in particular in railroad frog crossing applications.
Frog railroad crossings generally refer to the crossing point of two rails. A railroad frog typically forms part of a railroad switch, and is also used in a level junction, also referred to as a flat crossing.
Such frog railroad crossings have historically presented problems because of the substantial weight and vibration applied to such frog crossings when trains pass over such rails. The substantial weight and vibration caused by the passing over frog crossings by locomotives and railroad cars can have the effect of loosening the rail fasteners, thereby causing a dangerous condition.
Fluid operated torque tools are typically used to fasten frog crossing rails to underlying plates, which in turn are affixed to railroad ties. However, when tightening the nut to fasten the rail against the plate with a fluid operated torque tool, the torque applied is subject to reaction, and the usual reaction fixtures of such torque tools apply a very substantial amount of side load onto the nut to be tightened. The result is a change in the turning friction of the nut that changes and thereby reduces the torque of the tool. This causes frequent nut loosening and even disassembly of the rail crossing, which in turn can have the dangerous result of a locomotive or rail car running off the track.
An additional problem is that the side load runs through the tool mechanism, thereby making the torque tool subject to early failure.
In order to avoid the problems presented above, it is desirable to achieve a known torque within 3% accuracy, which requires a coaxial action and reaction. Torque tools having a coaxial action and reaction exist, but have the distinct disadvantage of having the reaction socket abut against the nut to be tightened.